108 lines
3.2 KiB
C++
108 lines
3.2 KiB
C++
#include <torch/csrc/autograd/function.h>
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#include <c10/util/ThreadLocal.h>
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#include <torch/csrc/autograd/engine.h>
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#include <torch/csrc/autograd/variable.h>
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#include <ATen/ATen.h>
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#include <algorithm>
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#include <cstdint>
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#include <memory>
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#include <stdexcept>
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#include <string>
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#include <utility>
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#include <vector>
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namespace torch {
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namespace autograd {
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// The current evaluating node. This is useful to assign the current node as a
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// parent of new nodes created during the evaluation of this node in anomaly
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// mode.
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C10_DEFINE_TLS_static(std::shared_ptr<Node>, tls_current_evaluating_node);
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#define current_evaluating_node (tls_current_evaluating_node.get())
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NodeGuard::NodeGuard(std::shared_ptr<Node> node) {
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last_evaluating_node_ = std::move(current_evaluating_node);
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current_evaluating_node = std::move(node);
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}
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NodeGuard::~NodeGuard() {
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// restore the previous evaluating node
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current_evaluating_node = std::move(last_evaluating_node_);
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}
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std::shared_ptr<Node> get_current_node() {
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return current_evaluating_node;
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}
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void Node::assign_parent() {
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metadata()->assign_parent(current_evaluating_node);
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}
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auto Node::name() const -> std::string {
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return c10::demangle(typeid(*this).name());
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}
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AnomalyMetadata* Node::metadata() noexcept {
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if (!anomaly_metadata_) {
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anomaly_metadata_ = Engine::get_default_engine().make_anomaly_metadata();
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}
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return anomaly_metadata_.get();
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}
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static void gatherFunctions(
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Node* func,
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std::vector<std::shared_ptr<Node>>& stack) {
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func->release_variables();
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for (auto& edge : func->next_edges()) {
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if (edge.function.use_count() == 1) {
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stack.emplace_back(std::move(edge.function));
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} else {
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edge.function.reset();
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}
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}
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}
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/*
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* Fix for #5534: prevent stack overflow on deletion of deep computation graph
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*
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* Sometimes one can end up with a very big computation graph of Nodes
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* and Edges. Each std::shared_ptr<Node> contains a list of Edge, and
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* each Edge contains a std::shared_ptr<Node>. Deleting a
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* std::shared_ptr<Node> can trigger the recursive deletion of other
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* std::shared_ptr<Node>'s: this can stack overflow if the graph
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* is deep enough. Here is an example of such a graph:
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*
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* shared_ptr<Node> -> Edge -> shared_ptr<Node> -> Edge -> ... ->
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* shared_ptr<Node>
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*
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* The solution here is to detect when we are decrementing away the last
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* reference to a Node, and when doing so to buffer up the Node's
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* that will be recursively decremented. We can then decrement (and free)
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* the original Node without causing a recursive cascade, before
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* draining the buffer applying the same behavior. This is, in effect,
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* converting recursion to a loop, using a heap buffer in place of the
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* recursive call stack.
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*/
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void deleteNode(Node* function) {
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// To avoid stack overflow on large computational graphs,
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// we need to track reference decrementing and freeing
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// on the heap.
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function->release_variables();
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std::vector<std::shared_ptr<Node>> stack;
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gatherFunctions(function, stack);
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delete function;
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while (!stack.empty()) {
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auto func = std::move(stack.back());
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stack.pop_back();
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gatherFunctions(func.get(), stack);
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// Reference count is decremented on the loop backedge.
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}
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}
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} // namespace autograd
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} // namespace torch
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